This invention relates to flame retardant compositions of enhanced effectiveness in which N,Nxe2x80x2-piperazinebis(neopentylglycol)phosphoramidate is utilized as a component. More particularly this invention relates to the use of certain additives in combination with N,Nxe2x80x2-piperazinebis(neopentylglycol)phosphoramidate and the use of such combinations in polymers, especially thermoplastic polymers, whereby achievement of enhanced flame retardancy is made possible.
U.S. Pat. Nos. 5,973,041, 6,221,939 B1 and 6,228,912 B1 show in Example 1 thereof that although N,Nxe2x80x2-piperazinebis(neopentylglycol)phosphoramidate (a.k a. N,Nxe2x80x2-bis(neopentylenedioxyphosphoryl)piperazine) exhibited satisfactory high temperature properties in polycarbonate as indicated by glass transition temperature (Tg) measurement, this compound was unsatisfactory as a flame retardant as it resulted in an unacceptably high total flame out time (FOT).
It would be of advantage if a way could be found of enhancing the effectiveness of N,Nxe2x80x2-piperazinebis(neopentylglycol)phosphoramidate as a flame retardant. This invention is deemed to fulfill this objective in an effective manner.
This invention involves the discovery, inter alia, that despite the poor flame retardancy performance of N,Nxe2x80x2-piperazinebis(neopentylglycol)phosphoramidate (a.k.a. N,Nxe2x80x2-bis(neopentylenedioxyphosphoryl)piperazine) as reported by the above three U.S. patents, combinations of this compound together with a melamine compound, make it possible to provide polymer blends having substantially improved flame retardant properties.
Moreover, in preferred embodiments this invention makes it possible to provide highly economical thermoplastic compositions that are entirely free of the environmental concerns attributed to halogen-containing additives and also antimony-containing components often used in polymeric materials. In addition, this invention makes it possible to provide flame retarded thermoplastic compositions in which the physical properties needed for end use applications are not materially impaired. In fact, in certain preferred embodiments, compositions having increased melt flow properties are provided.
Accordingly, this invention provides in one of its embodiments a flame retardant additive composition which comprises a blend of the following:
a) N,Nxe2x80x2-piperazinebis(neo-pentylglycol)phosphoramidate; and
b) at least one co-additive which is (i) melamine, (ii) one or more melamine compounds, or (iii) both of (i) and (ii).
Another embodiment is a resin composition comprising a thermoplastic polymer with which has been blended, singly and/or in admixture, a flame retardant amount of:
a) N,Nxe2x80x2-piperazinebis(neopentylglycol)phosphoramidate; and
b) at least one co-additive which is (i) melarnine, (ii) one or more melamine compounds, or (iii) both of (i) and (ii).
Preferably, but not necessarily, the above additive composition and resin compositions are halogen-free (as defined herein) and also antimony-free.
A further embodiment is a flame retardant resin composition comprising:
A) an acid-sensitive thermoplastic polymer;
B) N,Nxe2x80x2-piperazinebis(neopentylglycol)phosphoramidate that is free or essentially free of acid species; and
C) at least one co-additive which is (i) melamine, (ii) one or more melamine compounds, or (iii) both of (i) and (ii);
and/or any resultant reaction product or products thereof that are present in said composition.
The thermoplastic polymer compositions of this invention are characterized in that they are able to provide standard test specimens for the UL 94 test procedure having or giving at least a V-2 rating in said test procedure with standard test specimens of at least one of the following thicknesses: (1) {fraction (1/16)}-inch thickness or (2) xe2x85x9-inch thickness. Preferred compositions are those as just described in which the standard test specimens for the UL 94 test procedure of at least one of the thicknesses of (1) or (2) have or give a V-0 rating in that test procedure. Most preferably specimens of both such thicknesses have or give a V-0 rating. The UL 94 test procedure referred to herein is the procedure as published in Underwriters Laboratories Inc. Standard for Safety UL-94 xe2x80x9cTest for Flammability of Plastic Materials for Parts in Devices and Appliancesxe2x80x9d.
Other embodiments of the invention exist, and will be further apparent from the ensuing description and the appended claims.
A number of melamine compounds are deemed suitable for use in the practice of this invention. In this connection, by xe2x80x9cmelamine compoundxe2x80x9d or xe2x80x9cmelamine compoundsxe2x80x9d is meant an additive compound or additive compounds having at least one 6-membered triazine ring or moiety therein in which at least one amino nitrogen atom is directly bonded to at least one such triazine ring on a carbon atom of the ring. When the melamine compound contains more than one such ring or moiety, the rings or moieties can be in the form of fused ring structures (as in melem or melon) or unfused ring structures (as in melam). One type of candidate melamine compounds for use as co-additives of this invention are melamine and N-hydrocarbyl or N-halohydrocarbyl derivatives of melamine of the general formula: 
where each R is, independently, a hydrogen atom, a C1-6 alkyl group, a C5-6 cycloalkyl group, C1-6 haloalkyl group, a C5-6 halocycloalkyl group, a C6-12 aryl group, or a C6-12 haloar C7-12 aralkyl group, or a C7-12 haloaralkyl group. A few non-limiting examples of this type of melamine compounds include melamine, N-methylmelamine, N-cyclohexylmelamine, N-phenylmelamine, N,N-dimethylmelamine, N,N-diethylmelamine, N,N-dipropylmelamine, N,Nxe2x80x2-dimethylmelamine, N,Nxe2x80x2,Nxe2x80x3-trimethylmelamine, N-trifluoromethylmelamine, N-(2-chloroethyl)melamine, N-(3-bromophenyl)melamine, and the like. Also alcohol derivatives of melamine such as trimethylolmelamine or triethylolmelamine may be used. Melamine sulfate and melamine phosphates such as melamine orthophosphate, melamine polyphosphate, and dimelamine orthophosphate may also be used. Another useful melamine compound is melammonium pentate (i.e., the dimelamine salt of pentaerythritol diphosphate). Still other melamine compounds that may be used are melam, melem, and melon. Preferred melamine compounds are melamine pyrophosphate and melamine cyanurate, each of which is available commercially. Melamine can be used singly or in admixture with one or more other melamine compounds, provided the mixture is effective as a flame retardant. Likewise melamine compounds may be used singly or as mixtures of two or more melamine compounds, provided the mixture is effective as a flame retardant. Methods for the preparation of melamine compounds are known and reported in the literature. See for example U.S. Pat. No. 4,298,518; Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Edition, volume 7, pages 748-752; Id., volume 10, page 980; and E. Prill, J. Am. Chem. Soc., 1947, 69, 62.
A method for the preparation of N,Nxe2x80x2-piperazinebis(neopentylglycol)phosphoramidate (hereinafter sometimes referred to as PBNGP) has been reported in Japan Kokai 54/019919. A more practical process is described hereinafter.
It has been found that when using PBNGP as a flame retardant in an acid-sensitive substrate or host polymer such as polybutylene terephthalate, the presence of excessive acid species in the PBNGP can result in severe degradation of properties of the molded polymer, such as color, tensile strength, or the like. Such acid species can include free acids such as HCl or HBr, amine hydrohalide, and/or any acid or acidic impurities resulting for example from hydrolysis and/or other transformations occurring in the PBNGP product or the starting materials used in its synthesis. There are different ways of combating this adverse situation. One way is to add a sufficient amount of one or more acid scavenger additives to the polymer blend to negate the adverse effects of the acid species. A preferred way is to use PBNGP that is free or essentially free of acid species as determinable by use of nmr, mass spec, and/or HPLC. As shown hereinafter, if the PBNGP has been sufficiently washed with a suitable aliphatic halohydrocarbon solvent (and optionally separately with water as well) so that it is a snow-white product, it is likely that nmr, mass spec, and/or HPLC will show that the product is free or essentially free of acid species. Among the thermoplastic polymers that are acid-sensitive are polyesters, polyamides, polycarbonates, polycarbonate-ABS blends, and the like. In this connection, it is not presently possible to quantify the term xe2x80x9cessentially freexe2x80x9d because the small amount of acid species that can be tolerated in the polymer blend without encountering significant degradation in polymer properties will depend upon such factors as the particular polymer being used, the concentration of PBNGP being used, the temperature conditions under which the polymer is being processed, and the amount of degradation that is deemed acceptable under a given set of circumstances. Moreover, conventional criteria such as acid number have not been found applicable to PBNGP because of its extremely low solubility in water; conventional acid number titrations with KOH cannot be used. What can be stated is that the lower the content, if any, of acid species in the PBNGP, the better. Thus as used herein the term xe2x80x9cessentially freexe2x80x9d involves the application of a common sense approach, i.e., the PBNGP is essentially free of acid species if the amount of acid species that is present therein is insufficient to cause any unacceptable degradation in properties of the molded polymer composition. Accordingly, if nmr, mass spec, and/or HPLC indicates that acid or acidic species are present in the PBNGP, a representative sample of the PBNGP can be washed as described in Example 13 hereinafter until a snow-white PBNGP product having no detectable acid species in the dried product is formed. Then a pair of trial experiments should be carried out in which a given quantity of the original untreated PBNGP is blended into one portion of the selected substrate polymer, and the same quantity of the treated (washed and dried) acid-free PBNGP is blended into another identical portion of the same substrate polymer. Then the two blends should be separately molded under the same conditions into test specimens and physical properties of the respective specimens determined, using tests such as shown in Table 3 hereinafter. If the tests show that the untreated and the washed specimens have acceptable properties, the untreated PBNGP is deemed to be xe2x80x9cessentially freexe2x80x9d of acid or acidic species. But if the properties of the unwashed specimens are significantly degraded as to be unacceptable as compared to the properties of the treated specimen, the untreated PBNGP does not qualify as being xe2x80x9cessentially freexe2x80x9d of acid or acidic species.
Since the PBNGP is useful as a flame retardant in thermoplastic polymers that are acid-sensitive as well as thermoplastic polymers that are not acid-sensitive (e.g., polyolefin polymers) it is preferred that the PBNGP used in the practice of this invention is free or essentially free of acid species as determinable by use of nmr, mass spec, and/or HPLC. However in cases where PBNGP is to be used only in substrate thermoplastic polymers that are not acid-sensitive, the PBNGP need not be free or essentially free of acid species as determinable by use of nmr, mass spec, and/or HPLC.
Those of ordinary skill in the art of analytical chemistry have the knowledge and skills necessary for determining by use of nmr, mass spec, and/or HPLC whether the PBNGP is free or essentially free of acid species.
The relative proportions as between one or more melamine compounds (hereinafter sometimes referred to individually and collectively as xe2x80x9cco-additivexe2x80x9d) and PBNGP can vary. Preferably the weight ratio of PBNGP to co-additive will be in the range of about 0.1:1 to about 5:1, and more preferably in the range of about 0.2:1 to about 4:1. Still more preferably the weight ratio of PBNGP to co-additive will be in the range of about 0.5:1 to about 2:1. Departures from these ranges are permissible whenever deemed necessary or desirable without departing from the scope of this invention.
A flame retardant amount of the combination of PBNGP and co-additive is used in the thermoplastic polymer compositions of this invention. The term xe2x80x9cflame retardant amountxe2x80x9d as used herein, including the claims hereof, means that the total amount of PBNGP and co-additive used in forming the polymer blend is at least the minimum amount needed with the particular polymer with which PBNGP and co-additive are blended, whether blended singly and/or in admixture, to enable molded test specimens of at least one of the following thicknesses: (1) {fraction (1/16)}-inch thickness or (2) xe2x85x9-inch thickness to exhibit at least a V-2 rating in the UL-94 test procedure. Thus more than such minimum amount of PBNGP and co-additive relative to the amount of polymer can be used in these situations and be considered a flame retardant amount, provided that the weight ratio of PBNGP and co-additive to polymer is not so high as to make it impossible to prepare from such a blend molded specimens that are substantially uniform in composition from specimen to specimen and that have acceptable properties. On the other hand, in connection with masterbatch blends or powder preblends that are prepared for future dilution with additional polymer of (i) preparatory to making finished molded, extruded or foamed shapes or objects (articles), any amount of PBNGP and co-additive that is above the minimum xe2x80x9cflame retardant amountxe2x80x9d can be used. In connection with what constitutes a flame retardant amount, a V-1 rating is better than a V-2 rating and a V-0 rating is better than a V-1 rating, and thus the phrase xe2x80x9cat least a V-2 ratingxe2x80x9d means that the specimens satisfy the requirements of a V-2 rating, and may satisfy the requirements for a V-1 or V-0 rating, or both. Preferred compositions yield test specimens exhibiting at least a V-1 rating. Most preferred compositions yield test specimens exhibiting a V-0 rating.
Thermoplastic polymers with which the additives of this invention can be blended include such polymers as polystyrene; copolymers of two or more styrenic monomers such as styrene, vinyltoluene, ethylstyrene, tert-butylstyrene, a-methylstyrene, vinylnaphthalene, etc.; rubber-modified vinylaromatic homopolymers or copolymers (e.g., high impact polystyrene); styrenic copolymers such as ABS, SAN, MABS; thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polycyclohexylene terephthalate, etc.; thermoplastic polyamides, such as nylon 6, nylon 66, nylon 6,12, etc.; polycarbonates, polyphenylene oxides, such as poly(2,6-dimethylphenylene oxide); polysulphones; polyolefins, such as polyethylene, polypropylene, poly(1-butene), copolymers of ethylene with one or more higher vinyl olefins such as propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene; and blends or composites of different polymers such as for example a blend of poly(2,6-dimethylphenylene oxide) and polystyrene, a blend of poly(2,6-dimethylphenylene oxide) and HIPS, or a blend of aromatic polycarbonate and ABS.
Thermoplastic and thermoplastic elastomeric polyesters constitute a preferred type of polymer used in the practice of this invention. Non-limiting examples of such polyesters for use in this invention include poly(ethylene terephthalate), poly(1,3-propylene terephthalate), poly(1,4-butylene terephthalate), poly(cyclohexanedimethanol terephthalate), poly(cyclohexanedimethanol-co-ethylene terephthalate), polyethylene naphthalate, polybutylene naphthalate, and polyarylates. Illustrative, non-limiting examples of thermoplastic elastomeric polyesters (commonly known as TPE) include polyetheresters such as poly(alkylene terephthalate)s (particularly poly[ethylene terephthalate] and poly[butylene terephthalate]) containing soft-block segments of poly(alkylene oxide), particularly segments of poly(ethylene oxide) and poly(butylene oxide); and polyesteramides such as those synthesized by the condensation of an aromatic diisocyanate with dicarboxylic acids and a carboxylic acid-terminated polyester or polyether prepolymer. Poly(1,4-butylene terephthalate) (often referred to as PBT) is a particularly preferred substrate or host polymer.
Various thermoplastic polymers suitable for use in the practice of this invention can be obtained from a number of commercial sources.
The polymer compositions of this invention can be in the form of a preblend (e.g., a powder blend) comprised of the thermoplastic polymer, PBNGP, and co-additive, which can be molded or extruded under suitable temperature and pressure conditions to form a shape or object, whether foamed (expanded) or in non-foamed (non-expanded) condition. Likewise the compositions can be in the form of the molded or extruded shape or object itself. Also, the polymer compositions of this invention can be in the form of a masterbatch or concentrated preblend in which the concentration of the flame retardant components therein is higher than the intended concentration in the ultimate finished molded shape or object to be fabricated. Such masterbatch or concentrated preblend is mixed or blended with additional polymer either as dry materials or as a melt blend which is then molded or extruded to produce the finished shape or object.
When pursuant to this invention the flame retardant components above are blended in a flame-retardant amount into the thermoplastic polymer (preferably but not necessarily in the absence of any halogen-containing flame retardant additive, and also preferably but not necessarily in the absence of any antimony-containing additive component as well), the resultant polymer composition provides molded test specimens which exhibit at least a V-2 rating using standard test specimens that are at least of one of the following thicknesses: (1) {fraction (1/16)}-inch and (2) xe2x85x9-inch, if subjected to the well-known standard UL-94 test procedure. Preferred compositions of this invention exhibit a V-0 rating when using standard test specimens of at least one of the following thicknesses: (1) {fraction (1/16)} or (2) xe2x85x9-inch, if subjected to the standard UL-94 test procedure. As noted above, in forming the blends of this invention the individual flame retardant components (PBNGP and co-additive) can be separately blended with the substrate polymer. Preferably however, a preformed mixture of PBNGP and co-additive is employed in the blending operation. In this way the likelihood of blending errors is reduced, and in general the blending operation is rendered more facile.
The flame retarded polymer compositions can constitute finished polymer compositions containing a flame retardant amount of the flame retardants of this invention as defined above. Typically the total amount of the PBNGP and co-additive components blended into the substrate or host polymer will be in the range of about 10 to about 60 weight percent, although it is more desirable in most cases that the finished composition contains a flame retardant amount in the range of about 20 to about 55 weight percent. Thermoplastic polymer compositions containing a flame retardant amount of PBNGP and co-additive or their reaction products in the range of about 20 to about 50 weight percent are preferred. Particularly preferred are thermoplastic polymer compositions containing a flame retardant amount of PBNGP and co-additive or their reaction products in the range of about 25 to about 50 weight percent. In all cases the foregoing weight percentages are based on the total weight of the PBNGP and co-additive(s) used and of the substrate or host polymer(s) used in forming the flame retarded polymer composition. Therefore, the weight of other components, if any, used in making the flame retarded polymer composition is excluded from these ranges. In addition it is to be clearly understood that when it is indicated that the polymer xe2x80x9ccontainsxe2x80x9d a given quantity of an additive, such additive need not remain in the same chemical form as it existed prior to being introduced into the blending operation with the polymer(s) and/or other additive component(s). Such components may, especially during melt blending and/or during molding operations, enter into some type(s) of chemical reactions and/or other chemical changes or transformations. In short, the percentages of additive components should be read as one would read a recipe for making a cake. Certain specified amounts of things like yeast, flour, butter, eggs, salt, milk, and so on are blended together and the mixture is baked. No one really cares whether these ingredients still exist as such or whether they have lost their original chemical makeupsxe2x80x94the important things are that they were what they were when introduced into the mixture and that the overall result was favorable.
As noted above, one way of forming such polymer compositions is by use of masterbatch or additive-rich preblend compositions made from the substrate polymer and a higher percentage of the PBNGP and co-additive than the percentage to be included in the ultimate finished product. Such masterbatches or additive-rich preblend compositions will typically be a melt blended masterbatch or a powder preblend made from about 20 to about 90 parts by weight of the PBNGP and co-additive per hundred parts by weight of these flame retardants plus the substrate or host polymer(s). Such masterbatch and additive-rich preblend compositions, which constitute additional embodiments of this invention, can subsequently be used in forming finished polymer compositions by blending an appropriate amount of the masterbatch or additive-rich preblend with an appropriate amount of the substrate or host thermoplastic polymer(s) to thereby produce a blend having the desired end use proportions of the flame retardant components in whatever form they exist after being blended together.In preferred embodiments of this invention, no bromine- or chlorine-containing flame retardant additive component is intentionally added to the compositions of this invention. Consequently, preferred polymer compositions of this invention do not contain bromine or chlorine contents from flame retardant additives except for impurities which may occur therein as a consequence of the materials (solvents, catalysts, etc.), the process, or the process equipment used in the synthesis or manufacture of the polymer or in the synthesis of any of what purport to be bromine- or chlorine-free additive components that are used therein. Typically the preferred additive compositions, e.g., a masterbatch or preblend of the flame retardant components, which can be used in accordance with this invention to prepare preferred finished polymer compositions of this invention, will contain, if any, no more than about 1000 parts by weight of bromine and/or chlorine as impurities per million parts by weight (ppmw) of additive composition, and thus the term xe2x80x9chalogen-freexe2x80x9d in connection with such additive compositions means that they contain, if any, no more than about 1000 ppmw of bromine and/or chlorine. Preferred finished polymer compositions of this invention will typically contain, if any, no more than about 100 parts by weight of bromine and/or chlorine impurities per million parts by weight of the total polymer composition. Therefore, the term xe2x80x9chalogen-freexe2x80x9d as used herein in connection with preferred finished polymer compositions means that they contain, if any, no more than about 100 ppmw of bromine and/or chlorine. Usually they will contain less bromine and/or chlorine than this, unless a bromine- and/or chlorine-containing solvent or a bromine- and/or chlorine-containing halogen-containing gas is used in preparing the resin or a foam produced from a preferred polymer composition of this invention. These preferred halogen-free compositions of this invention can, however, contain fluorine-containing components such as polytetrafluoroethylene and/or related fluoropolymers as the term xe2x80x9chalogen-freexe2x80x9d as used herein applies only to bromine and/or chlorine.
Similarly, in preferred embodiments no antimony-containing additive is intentionally added to a composition of this invention. Such preferred compositions are devoid of antimony-containing components except possibly for adventitious trace amounts which possibly may find their way into the polymer blends through contamination of blending equipment by antimony additives such as antimony oxides previously used in such equipment.A further embodiment of this invention is the method of rendering a thermoplastic polymer flame resistant which comprises incorporating therein PBNGP and co-additive in an amount such that the resultant polymer composition contains a flame retardant amount of these components in whatever chemical composition and form such components exist in the resultant polymer composition. As noted above, such polymer composition can provide test specimens exhibiting at least a V-2 rating, and preferably a V-0 rating, in the UL-94 test procedure. It is possible to incorporate the PBNGP and co-additive in the substrate polymer prior to, or during, formation of the polymer. For example, such components may possibly be added to the monomer(s) or to the polymerization system to be used in forming the polymer. Similarly, it may be possible to add the PBNGP and co-additive to the polymerization mixture during the course of the polymerization reaction itself. Preferably however, the PBNGP and co-additive are added to the thermoplastic polymer after the polymer has been produced. It will also be appreciated that the possibility exists for additions being made in stages, such as prior to and during the polymerization, or prior to and after the polymerization, or during and after the polymerization, or prior to, during and after the polymerization.
Flame retarded thermoplastic polymer compositions of this invention such as thermoplastic polyesters and thermoplastic polyamides intended for use in applications where added strength and dimensional stability are of importance, preferably contain reinforcing amounts of at least one reinforcing agent or component. Non-limiting examples of such reinforcing agents or components include glass fibers, carbon fibers, metal strands or whiskers, and similar reinforcing materials. In certain applications use of glass fibers cut into two or more different lengths can be especially useful. Glass-reinforced thermoplastic polyesters flame retarded pursuant to this invention, such as flame retarded glass-filled or glass-reinforced PET or PBT, constitute particularly preferred reinforced thermoplastic compositions of this invention.
It is also within the scope of this invention to include one or more other phosphorus-containing flame retardants in the compositions of this invention. Non-limiting examples of other phosphorus additives which can be used include those described as useful flame retardants in U.S. Pat. Nos. 3,997,505; 4,007,236; 4,018,560; 4,053,450; 4,365,033; 4,373,103; 4,808,744; 5,973,041; 6,221,939 B1; and 6,228,912 B1.
Still other ingredients such as extrusion aids (e.g., barium stearate, magnesium stearate, or calcium stearate), dyes, pigments, fillers, stabilizers, antioxidants, antistatic agents, reinforcing agents, UV stabilizers, nucleating agents, acid neutralizers, polymer clarifiers, and the like can be included in the polymer compositions of this invention. U.S. Pat. No. 6,060,543, provides an extensive listing of typical polymer additives from which suitable additive components can be selected. For example, phenolic antioxidants can be found within the disclosure of that patent from Column 34, line 28 through Column 37, line 35. From Column 37, line 36 through Column 40, line 2 of that patent is a listing of UV absorbers and light stabilizers from which suitable components can be selected. Suitable metal deactivators or passivators can be found in the disclosure of that patent in Column 40, lines 3-12. The patent at Column 42, lines 31 through 38 lists nucleating agents, and at Column 42 from lines 39 through 43 lists fillers and reinforcing agents, from which components of these types can be selected. Suitable thiosynergists, peroxide scavengers, polyamide stabilizers, and basic co-stabilizers can be found within the listings at Column 41, lines 49 through 67, and Column 42, lines 29 and 30 of the patent. All of these passages of the patent are incorporated herein by reference with the caveat that each component that is selected from such listings must not in the amount used materially affect adversely the properties of the composition of this invention in which it is employed.
Non-limiting examples of nucleating agents which can be used are sodium 2,2xe2x80x2-methylenebis(4,6-di-tert-butylphenyl)phosphate, sodium adipate, sodium diphenylacetate, sodium benzoate, and talc. Non-limiting examples of polymer clarifiers which can be used include 1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol (Millad 3988; Millikan Chemical), 1,3 :2,4-bis-(p-methylbenzylidene)sorbitol (Millad 3940; Millikan Chemical), and 1,3 :2,4-di-O-benzylidenesorbitol (Millad 3905; Millikan Chemical).
Acid neutralizers or acid scavengers which can be, and preferably are used, in thermoplastic polymers, such as thermoplastic polyesters, in which trace amounts of acids may be released during thermal processing include such materials as tetrasodium pyrophosphate, zeolites, metal oxides (e.g., zinc oxide, magnesium oxide, and titanium dioxide), metal carbonates (e.g., calcium carbonate, and magnesium carbonate) and natural or synthetic hydrotalcites (e.g., magnesium hydrotalcites such as DHT-4A, DHT-4V, DHT-4C (all available from Kyowa Chemical Co.); Hysafe 539 and Hysafe 530 (available from J.M. Huber Corporation); L-55R acid neutralizers (available from Reheis Inc.); and zinc hydrotalcites such as ZH4-A (available from Kyowa Chemical Co.). Preferred acid neutralizers are magnesium hydrotalcites such as DHT-4A, DHT-4A2, DHT-4V, DHT-4C and Hysafe 530.
The hydrotalcite which is a preferred component in the practice of this invention, is preferably a monohydrotalcite or a dihydrotalcite, and such hydrotalcite is a magnesium-aluminum hydrotalcite, and may be represented by the following formula:
Mg1xe2x88x92x.Alx(OH)2.Ax/2.MH2O
wherein x stands for a value greater than 0 but equal to or smaller than 0.5 (0 less than xxe2x89xa60.5), A represents CO32xe2x88x92 or SO42xe2x88x92, and M stands for a positive value.
In general, the hydrotalcite is preferably a magnesium-aluminum composite hydroxide carbonate salt, and is more preferably represented by the general formula:
Mg6.Al2(OH)16.CO3.8H2O
wherein g is 0 or has a positive value. Hydrotalcite may also be represented by the following formula:
Mx.Aly.(OH)2x+3yxe2x88x922z.(A)z2H2O
wherein M represents Mg, Ca or Zn, A denotes CO3 or HPO4, x, y, and z stand for positive values.
The empical formulas as given by a commercial supplier for several of the preferred hydrotalcites that can be used are as follows:
Mg4.5Al2(OH)13.CO3
Mg4.5Al2(OH)13.CO3.3H2O
Mg4.5Al2(OH)13.CO3.3.5H2O
Mg4.5Al2(OH)13.O0.2(CO3)0.8
Various known procedures can be used to prepare the blends or formulations constituting the compositions of this invention. For example the components to be incorporated into the finished blend can be blended together in powder form and thereafter molded by extrusion, compression, or injection molding. Likewise the components can be mixed together in a Banbury mixer, a Brabender mixer, a roll mill, a kneader, or other similar mixing device, and then formed into the desired form or configuration such as by extrusion followed by comminution into granules or pellets, or by other known methods.
The compositions of this invention can be utilized in the formation of useful articles of the type normally fabricated by molding or extrusion of conventional flame retarded polymers. Likewise it is possible to prepare foamed or expanded shapes and objects from the compositions of this invention. Molding and extrusion conditions such as temperatures and pressures are within conventional recommended limits. Conditions normally used for producing foamed or expanded shapes and objects from flame retarded ABS can be used with the compositions of this invention, with little or no modification.